I liked using an air riffle to the head followed by sharp axe to cut head off. I read on here last year that sometimes it can miss the brain. I didn't believe this when I read it, given that I shoot rabbits and pigeons at range and they die.
I was sickened when I had a large cock who was not knocked unconscious by the pellet and my air riffle is a single shot, so had to quickly decapitate rather than reload. It was still over within seconds, but not good, and think its worth making people aware. I read that it can happen because the vital areas of brain are very small?
I have gone back to thump with back of axe rolled by sharp edge... Wearing my oilskin waterproofs.